Showing papers in "Geochimica et Cosmochimica Acta in 2003"

TL;DR: In this article, a new, accurately dated 250-kyr δ18O and δ13C record determined from speleothems of the Peqiin Cave, Northern Israel is presented.

TL;DR: In this paper, a noniterative procedure is presented to calculate the composition of the compressed CO 2 and liquid H 2 O phases at equilibrium, based on equating chemical potentials and using the Redlich-Kwong equation of state to express departure from ideal behavior.

TL;DR: In this article, the authors predicted the relative energies and geometries of AsO4-FeOOH surface complexes using density functional theory calculations on analogue Fe2(OH)2(H2O)nAsO2(23+) and Fe2 (OH) 2(H 2O) nAsO4+ clusters, and they found no evidence for monodentate (1V) complexes; this agrees with the predicted high energies of such complexes.

TL;DR: In this paper, the acid-base properties of 14 standard and reference materials from the International Humic Substances Society (IHSS) were investigated by potentiometric titration.

TL;DR: In this article, the authors investigated the pathways and mechanisms of secondary mineralization during dissimilatory iron reduction by a common iron-reducing bacterium, Shewanella putrefaciens (strain CN32), of 2-line ferrihydrite under advective flow conditions.

TL;DR: In this paper, the presence of zircon and rutile in the vein is another example of high field strength element (HFSE) mobility over short distances in aqueous fluids at eclogite-facies conditions.

TL;DR: In this paper, the most important steps in the overall process of the pyrite oxidation were mapped to the cathodic sites, where oxygen atoms from water molecules attach to the sulfur atoms to form sulfoxy species, through the crystal to cathodic Fe(II) sites where they are acquired by the oxidant species.

TL;DR: In this article, the structure and composition of the Mn oxide produced by Pseudomonas putida were characterized as to composition, average Mn oxidation number, and N2 specific surface area, and a series of synthetic Mn oxides also was analyzed by the same methods to gain better comparative understanding of the structure of the biogenic oxide.

TL;DR: In this paper, an ArF excimer laser system with imaging optics for controlled UV ablation and simultaneous petrographic viewing was designed specifically for representative sampling and quantitative multi-element analysis of microscopic fluid, melt and mineral inclusions beneath the sample surface.

TL;DR: Experimental diffusion couples were made by juxtaposing powders of a natural basalt and a natural rhyolite and then annealing them in a piston cylinder apparatus for times ranging from 0.1 to 15.7 h, temperatures of 1350-1450°C, and pressures of 1.2-1.3 GPa as mentioned in this paper.

TL;DR: In this paper, surface reaction controlled basaltic glass dissolution rates at far-from-equilibrium conditions were quantified, and the dissolution rates were interpreted within the context of a multioxide dissolution model.

TL;DR: In this paper, the authors investigated reactions of As(III) with iron sulfide and pyrite (FeS2) as a function of total arsenic concentration, suspension density, sulfide concentration, pH, and ionic strength.

TL;DR: In this article, a mechanism for vital effects in these deep-sea corals that is based on a thermodynamic response to a biologically induced pH gradient in the calcifying region is proposed.

TL;DR: A numerical model was applied to investigate and quantify biogeochemical processes and methane turnover in gas hydrate-bearing surface sediments from a cold vent site situated at Hydrate Ridge, an accretionary structure located in the Cascadia Margin subduction zone as mentioned in this paper.

TL;DR: In this article, the authors assess the oxidation state of altered ocean crust and estimate the magnitude of microbial biomass production that might be supported by oxidative and nonoxidative alteration, and estimate that 50% of Fe oxidation may be attributed to hydrolysis, producing 4.5 ± 3.0 × 1011 mol H2/yr.

TL;DR: Zhang et al. as mentioned in this paper showed that the interaction of the slab-derived silicic melt with the old refractory lithospheric mantle converted the Paleozoic cratonic lithosphere into the late Mesozoic fertile mantle, which was also different from the Cenozoic counterpart.

TL;DR: In this article, the main scope of the study is to investigate parameters controlling chemical weathering rates for a large river system submitted to subarctic climate, and more than 110 river samples from the Mackenzie River system (northern Canada) have been sampled and analyzed for major and trace elements and Sr isotopic ratios in the dissolved phase.

TL;DR: A comparison of published calcite dissolution rates measured far from equilibrium at a pH of ∼ 6 and above shows well over an order of magnitude in variation Recently published AFM step velocities extend this range further still.

TL;DR: The results of the mixing calculation indicate that terrigenous OM (soil-derived OM and vascular plant debris) accounts for ∼79% of the organic matter (OM) deposited as inshore sediments and 66% of OM deposited as offshore sediments as mentioned in this paper.

TL;DR: In this article, the authors define a nearly continuous record for the Late Permian and Triassic intervals, based on brachiopods and conodonts, and show that the rate of change in the 87Sr/86Sr values is 1.3 × 10−3.

TL;DR: In this article, the authors used cosmogenic nuclides together with a geochemical mass balance of weathered soil and parent rock to measure long-term chemical weathering and physical erosion.

TL;DR: In this paper, the authors employed the Attenuated Total Reflectance Fourier transform Infrared (ATR-FTIR) spectroscopy to investigate mechanisms of boric acid and borate adsorption on hydrous ferric oxide (HFO).

TL;DR: In this paper, a transect off the West African coast has been investigated for their lipid content and compound-specific stable carbon isotope compositions, and the results show that only regions with a predominant C4 type vegetation, i.e., the Sahara, the Sahel, and Gabon, supply C4 plant-derived lipids to dust organic matter.

TL;DR: Olivine (Fo89), orthopyroxene (En85), and clinopyroxenes (Di89) were reacted with NaCl-MgCl2 at 400°C, 500 bars to better assess alteration and mass transfer in ultramafic-hosted hydrothermal systems at mid-ocean ridges.

TL;DR: In this paper, bitumens extracted from 2.7 to 2.5 billion-year-old (Ga) shales of the Fortescue and Hamersley Groups in the Pilbara Craton, Western Australia, contain traces of molecular fossils.

TL;DR: In this paper, the Humic Ion-Binding Model V was modified to assess the role of dissolved natural organic matter in the speciation of rare earth elements (REEs) in natural terrestrial waters.

TL;DR: In this paper, lead sorption efficiencies were measured for a number of natural and synthetic Mn and Fe-oxides using a flow-through reactor, and the results showed that the synthetic Mn-oxide phases have higher sorption efficiency than the natural Mn-oxide phases, while the natural pyrolusite and hematite were significantly less reactive.

TL;DR: In this article, the evolution of clay-associated organic matter was followed from bedrock source to the seabed in the Eel River sedimentary system of northern California using natural abundance 13C and 14C tracers, and it was shown that approximately half of the fine-grained organic carbon delivered to the shelf is derived from ancient sedimentary organic carbon found in the uplifted Mesozoic-Tertiary Franciscan Complex of the watershed.

TL;DR: In this article, the average relative molar abundance of major cations and Si in all stream waters was investigated by analyzing the elemental and Sr isotope geochemistry of stream waters, bedload sediment, and hydrothermal calcite veins.

TL;DR: In this paper, the systematics of Cl, F and H2O in Izu arc front volcanic rocks using basaltic through rhyolitic glass shards and melt inclusions (Izu glasses) from Oligocene to Quaternary distal fallout tephra were studied.